Blade servers are self-contained all inclusive computer servers, designed for high density. Whereas a standard rack-mount server has a power supply and networking capability, blade servers have many components removed for space, power and other considerations while still having all the functional components to be considered a computer (i.e., memory, processor, storage).
The blade servers are housed in a blade enclosure. The enclosure can hold multiple blade servers and perform many of the non-core services (i.e., power, cooling, networking) found in most computers. Non-blade computers require components that are bulky, hot, and space-inefficient. By locating these services in one place and sharing them amongst the blade servers, the overall component utilization is more efficient.
Computers typically need bulk data storage to store operating systems, applications, and data for the server system. This bulk storage of data is typically accomplished with magnetic hard drives. One or more hard drives can be located in the enclosure or connected to it over a network. Hard drives add bulk, heat, and complexity from moving parts that are more prone to failure.